1. Field of the Invention
This invention relates to tractor and trailer combinations in heavy trucks. In particular the present invention provides a system for adjusting weight distribution throughout all axle groups of the truck and trailer.
2. Description of the Prior Art
The weight of a vehicle is of crucial importance in the trucking industry. The cost of delivering a load for commercial purposes is often assessed to the customer according to the weight of the load and the distance it must travel. Knowledge of load weight is therefore necessary to ensure that the customer is assessed the full price of transporting the load. Weight information can also be used to optimize the load at or near the vehicle's maximum capacity.
The weight of commercial trucks is also important from the perspective of public safety and highway maintenance. Overloading a commercial vehicle can create a hazard by reducing the truck's stability and braking ability. An overloaded commercial vehicle also causes significantly greater wear to public highways and to the vehicle itself. Governments therefore regulate vehicle weight by specifying a maximum legal load limit and fining vehicle operators for any overage.
Governments also regulate the weight of every axle group of a truck and/or trailer over the pavement. The axle groups on the trailer typically include one or more mounted on a suspension slider so they can be moved back and forth. By moving the suspension slider back and forth the cargo weight can be distributed between the axle group(s) on the trailer and the tractor so no one axle will be over the limit. When the trailer suspension slider is moved forward (closer to the truck) the weight is shifted from the tractor to the trailer (the trailer axle load weight becomes heavier and the tractor axle weight becomes lighter). When the trailer suspension is moved backward (away from the truck) the weight is shifted from the trailer to the tractor (the trailer axle load weight becomes lighter and the tractor axle weight becomes heavier). Very often the operator has to move the suspension back and forth to evenly distribute the weight to meet the compliance of the maximum axle load weight.
Moving the suspension slider for the axle group back and forth is not an easy or pleasant task and typically involves following several steps and considerable time. First the operator parks the tractor and trailer. Then he/she goes to the back of the trailer suspension and releases the lock/latch pins. Sometimes these pins are bound by the weight of the suspension and are difficult to release manually. This may require the driver to have to rock the trailer to disengage. The driver must then go back into the cab, move the tractor forward or backward so the suspension slider on the trailer is in the desired position. The operator then attempts to re-lock the pins, which could again require rocking the tractor to re-lock the pins. After the desired position of the suspension is attained, the driver must go back, physically lock the pins and visually inspect the suspension.
Without any means to measure or determine the weight on the axle groups, the position of the slider is chosen from guidelines and the driver's experience based on the load and the positioning of the load. Sometimes the judgment of the driver may prove to be incorrect which could result in overweight of one axle group over another.
Efforts to provide a solution to the problem have resulted in all or some of the functions done independently from each other for the purpose of displaying the axle group weight or calculating the Gross Vehicle Weight (GVW). Given the axle group weight, the driver can manually adjust the suspension between the truck and trailer.
One of the biggest problems with existing systems is the limitation of the response time of the air suspension systems. The known weight systems have employed various devices for sensing the weight of the vehicle including load cells, string gages, displacement transducer and so on. Most widely used are systems based on the measurement of the pressure in the air bag on the axle suspension and mathematical functions that can be done to convert to a weight. The problem is that there is often a relatively long period of time needed for the air bag to balance itself when the load is changed. When the weight is taken away, the air leveler in the air bag needs to release some air for the new weight and that process can take 2-3 minutes depending upon the amount of air pressure needed to be released. When weight is added, the pressure on the air bag needs to increase so the level mechanism can add air. After balancing, the air is cut off and then an accurate measurement of the pressure can be taken. The time required for the measurement of the weight on the air suspension can make the adjustment of the axle group or fifth wheel connection a long process because after every movement of the slider for the axle group or fifth wheel connection, the operator needs to wait a period of time (time for the air in the airbag to be balanced) and then measurement can take place.